Dual-culture tests with Trichoderma isolates and wood decay fungi
Interactions in wood
Application of Trichoderma spp. for the biological control of wood decay fungi on trees
Trees play an important role in ecology of human habitats in many ways: they filter air, water, sunlight, provide shelter to animals and recreational area for people. However anthropogenic stressors such as pollutants, drought stress, nutrient deficiency and regular pruning operations reduce the vitality and predispose trees for infection by wood decay fungi. Objective of this study was to evaluate the potential of different Trichoderma spp. as biocontrol agents of important wood decay fungi. For this purpose the potential of a range of Trichoderma isolates were examined in laboratory and field studies. Initially dual-culture tests on artifical growth media and wood were conducted to evaluate the antagonistic potential of different Trichoderma spp. against wood decay fungi that colonise pruning wounds.
Application of T-15603.1 on fresh pruning wounds. A: The conidial suspension 1 and 2 were sprayed onto the wound surface. B: The third type of spore suspension containing the carrier substance sodiumpolyacrylate was applied with a conventional brush.
The main objective of the field studies was to develop a treatment method that promotes colonization and survival of a selected Trichoderma isolate in pruning wounds. Trichoderma atroviride T-15603.1 was applied to pruning wounds with the following different spores suspensions:
A total of 196 trees and 1764 pruning wounds were treated.
- A: Suspension [CFU: 106 spore/ml]
- B: Suspension [CFU: 106 spore/ml +0,2% glucose + 0,1 % urea]
- C: Suspension [CFU: 106 spore/ml + 0,2% glucose + 0,1 % urea + 0,4 % Luquasorb® (sodium polyacrylate)]
- K: Control – no treatment
Left: Re-isolations of fungi were performed along a gradient (1, 3, 5cm) and from the sapwood [S]. The extracted wood samples were incubated on MEA, T.MEA and TSM. Discolouration was measured in the axial and radial direction (a, b). Right: Wounds that were treated with T-15603.1 showed a significantly lower rate of wood discoloration than control wounds.
The most important results can be summarized as followed: Trichoderma isolates showed a highly antagonistic potential against wood decay fungi in the in vitro studies. Method C using a water absorbing gel as carrier substance allowed Trichoderma isolate T-15603.1 to survive in the wood of pruning wounds. The extent of wood discoloration from pruning wounds was significantly lower after treatment with T-15603.1 then with control wounds. Pruning wounds from trees treated with T-15603.1 and subsequently inoculated with wood decay fungi i.e. Inonotus hispidus, Ganoderma adspersum and Polyporus squamosus were significantly lower infected than trees with untreated wounds.
Left: Re-isolation rates of T-15603.1 from the site in Ludwigshafen (BASF). Even 30 months after treatment, (C) T-15603.1 could be isolated at rate of approx. 75%. Right: Significant reduction in the inefection rate of pruning wounds by three wood decay fungi after treatment with T-15603-1.